China's energy regulator expects maximum power load this summer to swell by more than 100 million kilowatts from last year, threatening to strain supply in some regions, especially in harsh weather, it said on Monday.

The National Energy Administration (NEA) expects supply to be tight in eastern, central, southern and southwestern provinces and Inner Mongolia, particularly if the weather proves extreme, officials told a press conference.

Southwestern forest fires early this year have had a "serious effect" on the safe functioning of the power grid, said Yan Xiuwen, director of the NEA's office of power safety regulation.

A Feb 5 fire in the city of Liangshan in Sichuan province forced the closure of three transmission lines, cutting 11.2 million kilowatts of hydropower capacity from the main grid, "greatly affecting the regional power balance," Yan added.

From Feb. 17 to 22, a fire in Guizhou province forced the shutdown of as many as 14 high-voltage power lines, resulting in suspension of operations by three power plants.

China's State Council, or cabinet, has told the NEA to guard against large-scale power outages, Yan said, adding that it would participate in stepped-up fire prevention efforts by forestry and emergency officials. (Reporting by Colleen Howe; Editing by Clarence Fernandez)